Sgs-thomson Microelectronics S.r.l.

Sgsates Componenti Elettronici S.p.a.

Sgs Microelettronica Spa

Rinaldo Graziadei

Giorgio Rossi

Marco Siligoni

Michelangelo Lorusso

Michaelango Lorusso

Luigi Anzini

An integrated coupling circuit for coupling a modulator to a ceramic filter in amplitude modulation receivers, which modulator includes an output stage comprising a pair of differential cells parallel-connected to each other. The coupling circuit comprises a pair of transistors connected to each other through their respective bases and forming a bridge circuit with a diode and third transistor. Each transistor in the pair is connected in a cascode configuration and powered from a respective current mirror circuit connected to an output terminal of the modulator.

Integrating coupling circuit for coupling a modulator to a ceramic

A mixer dynamic control (MDC) system for an AM superheterodyne receiver prevents saturation of the mixer stage caused by out-of-tune signals much more effectively than a so-called wide band RF-AGC system of the known art. The system contemplates detecting the converted IF signal before the band filter, amplifying the detected signal, extracting the dc component thereof and summing such a dc component to a dc control signal generated by a narrow band AGC and applying such a sum signal in lieu of the sole narrow band AGC system's control signal.

Mixer dynamic control

The input stage of a radio receiver incudes a differential amplifier circuit, whose gain is adjusted by a voltage generated by an AGC circuit, and a mixer circuit. An attenuator stage with a predetermined attenuation coefficient is coupled between the input terminal of differential circuit and the input terminal of the mixer circuit. When the level of the input signal increases beyond a given value, the differential amplifier circuit is deactivated and the signal reaches the mixer circuit through the attenuator stage.

Transistor amplifier and mixer input stage for a radio receiver

A transistor mixer and amplifier input stage which includes a mixer and a differential amplifier whose gain is controlled by a voltage generated by an AGC circuit. Two transistors, each having a resistor connected in series with its emitter, are connected between the inputs of the differential amplifier and the mixer. When the level of the input signal increases beyond a given level, the two transistors begin to conduct, thereby shunting the differential amplifier.

Transistor mixer and amplifier input stage

Two cascaded capacitors, one in series and the other in shunt with a load, are connected across a source of amplitude-modulated oscillations with interposition of a small resistance, preferably the forward resistance of a series diode. The junction (A) of that resistance with the series capacitor is connected to the emitter of a transistor whose collector is energized with a high driving voltage (positive in the case of an NPN transistor) and whose base is tied to a tap on a voltage divider inserted between that collector and the opposite, usually grounded source terminal. The section of the voltage divider between the base and ground may consist of the forward resistance of a single diode, designed to balance the base/emitter threshold of the transistor whereby the aforementioned junction (A) is at ground potential when the source voltage peaks with a polarity opposite that of the collector potential. A biasing battery may be inserted between the voltage divider and ground to provide a voltage pedestal of the same polarity as the collector potential.

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Monza, Italy

Rinaldo Graziadei